Methane and N2O emissions, nitrate concentrations of drainage water, and zinc and copper uptake by rice fertilized with anaerobically digested cattle or pig slurry

We have examined the effects of different types of slurry on CH4 and N2O emissions, Zn and Cu contents of rice, and nitrate content of the drainage water. The experiment included four treatments: (1) anaerobically digested cattle slurry (ADCS), (2) ADCS filtered to remove the coarse organic matter fraction, (3) anaerobically digested pig slurry (ADPS), and (4) chemical fertilizer (CF). The application rate was 30 gNH(4)-N m(-2). Different amounts of C were incorporated with fertilization: 725 gC m(-2) in ADCS, 352 gm(-2) in filtered ADCS, and 75 gm(-2) in ADPS. The average CH4 emissions during a growing period were 304, 359, 452, and 579 mg m(-2) day(-1) in the CF, ADPS, filtered ADCS, and ADCS treatments, respectively. The CH4 emission was significantly higher in ADCS than in CF and ADPS. Negligible N2O emissions were observed during the growing period. Comparable concentrations of Zn and Cu were observed in the rice grain among the treatments. In contrast, their concentrations in the stems and leaves were significantly higher in ADPS than in CF treated rice, although the values were lower than the upper limit of feed additives. Nitrate concentrations in the drainage water were consistently low (0.5 mg NL-1). The present study suggested that ADPS, containing a lower amount of C than ADCS, might be an organic fertilizer in paddy field with comparable environmental impacts to chemical fertilizers (CF), but longterm field studies are needed to better understand the effects of these organic fertilizers.